1. Field of the Invention
The invention relates to an intake path gas introducing device that introduces gas from outside an intake path of an intake manifold into the intake path of the intake manifold of an internal combustion engine in which the intake gas is distributed into intake ports of two banks and to an internal combustion engine having the intake path gas introducing device disposed therein.
2. Description of the Related Art
As a configuration of a device that introduces gas into an intake path, for example, an exhaust gas recirculation device (EGR device) is available in which an exhaust circulation passage is led to an intake manifold and gas is introduced from an introducing passage formed integrally with the intake manifold into each intake path (see, for example, Japanese Patent Application Publication No. 6-81721 (JP-A-6-81721) (pages 4 and 5, FIGS. 1 to 3), Japanese Patent Application Publication No. 6-50216 (JP-A-6-50216) (page 3, FIGS. 1 to 4, 6, 8, and 9), Japanese Patent Application Publication No. 10-122071 (JP-A-10-122071) (pages 3 and 4, FIGS. 3 to 5), and Japanese Patent Application Publication No. 7-259657 (JP-A-7-259657) (page 3, FIG. 1). In the two-bank internal combustion engines described in these patent documents, space is saved by forming the exhaust introducing passages between the arrays in a zone where the intake manifold is divided into two arrays.
However, in the configurations described in JP-A-6-81721 and JP-A-6-50216, exhaust gas introducing passages are integrated so as to belong to respective two divided manifold arrays, and the exhaust gas introducing passage is completely separated for each intake manifold. As a result, the exhaust introducing passages do not reinforce the entire intake manifold, and stresses generated between the two manifold arrays can be concentrated between the exhaust gas introducing passages.
In the configurations described in JP-A-10-122071 and JP-A-7-259657, a common exhaust gas introducing passage is formed for two divided manifold arrays. However, in the configuration described in JP-A-10-122071, the exhaust gas introducing passage (gas reflux passage 40 in FIGS. 4 and 5 of JP-A-10-122071) is formed as a pipe with respect to the intake manifold, and branch tubes extend from this pipe to each intake manifold alternate, thereby distributing the exhaust gas. As a result, the exhaust introducing passages do not reinforce the entire intake manifold, and stresses generated between the two manifold arrays can concentrate in the connection portions of the intake manifolds and small branch tubes.
In the configuration described in JP-A-7-259657, a wall portion of an exhaust gas introducing passage (chamber 37 shown in FIG. 1 of JP-A-7-259657) is formed to protrude significantly at an acute angle downward, as if hanging down, with respect to a wall portion of an intake manifold (individual intake path 6 shown in FIG. 1 of JP-A-7-259657), and stresses generated between the two manifold arrays can concentrate in a gap portion between the wall portion of the exhaust gas introducing passage and the wall portion of the intake manifold.
Therefore, in the configurations described in JP-A-6-81721, JP-A-6-50216, JP-A-10-122071, and JP-A-7-259657, stresses generated between the two manifold arrays can easily concentrate, and the entire intake manifold cannot be said to be reinforced.